Nanoprecipitate improves high strain-rate deformability in a high-entropy alloy

Improving the yield strength (YS) and work hardening of FeNiCoCr-based high entropy alloys (HEAs) at high-strain-rates (HSR) can meet the needs of applications such as automotive, bridge, and marine. In the present work, a new Fe₂₀Ni₃₀Co₂₀Cr₂₀Al₅V₅ nanoprecipitate-strengthened HEAs was developed, and the quasi-static compressive, dynamic-compressive properties, as well as its dynamic-deformation mechanism, were systematically investigated. The results show that nanoprecipitate-strengthened HEAs exhibit excellent dynamic mechanical properties. When the strain rate is 3750 s⁻¹, the YS of the HEAs with nanoprecipitates is 1383 MPa, which is 3 times that of the counterpart without nanoprecipitates, possessing an excellent strain rate strengthening effect. The grain size of the HEAs with nanoprecipitates is twice of that without nanoprecipitates after HSR deformation. The presence of nanoprecipitates suppresses the intragranular slip of dislocations, preventing the accumulation of dislocations to form subgrain boundaries and hindering grain refinement. The interaction between nanoprecipitates and stacking faults inhibits the expansion and rearrangement of stacking faults and delays the appearance of deformation twins (DTs) until the strain rate of 3750 s⁻¹, at which the twin width in HEA with nanoprecipitates is significantly narrower than that without nanoprecipitates. Narrower DTs can better hinder dislocation movement, reduce dislocation slip paths, enhance the dynamic Hall–Petch effect, and improve the work-hardening ability of HEAs at HSR.